Catamarans and trimarans, being normally unballasted, float with great
stability either way up. A float at the masthead should prevent the immersion
of the mast, and thus ensure that the craft never gets into the stable, inverted
attitude. Some floats are made of lightweight foamed plastic, or are
air-fIlled hollow chambers. Others are bladder-like, to be inflated
automatically from a carbon dioxide cylinder if the boat goes beyond a certain
angle of heel.